1. Field of the Invention:
This invention relates in general to subsea well assemblies, and in particular to means for reducing rocking movement between a wellhead and a wellhead housing, and thereby increasing the ability to transfer wellhead loads to the wellhead housing.
2. Description of the Prior Art:
In a subsea oil and gas well of the type concerned herein, a template is located on the sea floor. A wellhead housing is cemented into the sea floor and locates in the template. The wellhead housing is a large tubular member secured on its lower end to a large diameter conductor pipe that extends down into the sea floor a selected distance. A wellhead is lowered into the wellhead housing. The wellhead has on its lower end casing which extends down to a greater depth. The upper end is adapted to receive riser conduit that extends to the surface.
The riser conduit is subject to rocking movement due to movement of the vessel overhead and also wave action and currents. This rocking movement can extend downward into the wellhead. The wellhead will have a clearance between its outer wall and the bore of the wellhead housing. The rocking movement causes the wellhead to rock or bend relative to the wellhead housing. There is a lack of any rigid support between the wellhead and the housing resulting in an area in the wellhead where fatigue failure may occur.
There have been proposals to support the wellhead in the housing in a manner such that any bending forces are transmitted to the housing, reducing the rocking movement of the wellhead in the housing. One such proposal is shown in U.S. Pat. No. 4,499,950, Bruce J. Watkins, Feb. 19, 1985. While this patent and proposal is feasible, improvements are desired.